This has worked. Im going to submit a patch to my distro (gentoo) to fix this problem. Do you plan on supporting external avahi libraries in the future? How I fix the build script depends on that answer.
Once again I want to thank for your time and support!

We already do with 3.3, using the native avahi interface. Even the avahi website itself recommends to not use the old Apple-compatible interface anymore. I left the legacy stuff in for someone from Apple to pick it up and fix it. But so far nobody has volunteered, so Mac OS/X seems not so important anymore these days.
Volker